An image coding method for generating coded data by subjecting image data to lossless coding, is well known. As the image coding method of conventional technique, by switching a prediction direction for each pixel based on a gradient of pixel values between adjacent pixels, a difference of pixel values between a coding target pixel and a prediction pixel is coded (encoded). However, in this method, each pixel is subjected to coding (encoding). Accordingly, coding cannot be effectively performed.
As another image coding method of convention technique, by segmenting an input image into a plurality of pixel blocks, each pixel block is decided whether to code or skip. However, based on a size of the pixel block, effective coding cannot be often performed.
As the other image coding method of conventional technique, by calculating a prediction pixel for each pixel block, each pixel is decided whether to code or skip. However, in this method, each pixel is decided. Accordingly, coding cannot be quickly performed.
Briefly, in this technical area, an apparatus for quickly and effectively coding an image is desired.